1. Field of the Invention
The present general inventive concept relates to a method and apparatus to encode a speech signal and a music signal and a method and apparatus to decode a speech signal and a music signal.
2. Description of the Related Art
Conventional methods of coding a speech signal and a music signal include a transform coding method, a code excited linear prediction (CELP) coding method, and a hybrid transform and time domain coding method.
The transform coding method compresses a signal by applying a psycho-acoustic model in a frequency domain. Therefore, the quality of a speech signal may deteriorate. On the other hand, the CELP coding method compresses a signal by applying a speech production model in a time domain. Therefore, the quality of a music signal may deteriorate. The hybrid transform and time domain coding method removes temporal redundancy by applying the speech production model in the time domain and then compresses a residual signal in the frequency domain. Therefore, when the hybrid transform and time domain coding method is used, a lower sound quality may be achieved than when the transform coding method or the CELP coding methods is used.